1. Field of the Invention
The invention is situated in the field of good piece conveyance and is related to a device which serves for establishing an imbricated stream of flat articles, in particular of printed products such as, e.g., newspapers magazines or brochures.
In the printing industry, intermediate or partial products or also virtually finished products are subjected to various further processing steps. In certain devices intended for such further processing steps, for example, in cutting devices, it is advantageous to process such products lying on top of one another in groups. Imbricated streams accruing from such further processing steps are then streams of imbricated stacks, in which streams every scale is a stacked product group of, for example, two products. If, for example, the products of such a stream of imbricated stacks are to be counted, addressed or stacked and packaged independent of the group size, the stream of imbricated stacks has to be transformed into a stream of imbricated single products, i.e., into an imbricated stream, in which every scale consists of one product only. For other processing steps it may also be necessary to transform a simple imbricated stream into a stream of imbricated stacks or to make the spacings in a simple imbricated stream more uniform.
2. Description of Related Art
A device for extending printed product pairs being supplied in an imbricated stream (stream of imbricated stacks) is known from EP 0 075 121 B1. The stream of product pairs in which the pairs are transported on a conveyor belt at a first speed and in a formation in which in the manner of roof tiles the leading edge of each pair is lying on top of the preceding pair, is transformed into a stream of imbricated individual products being transported, for example, at double the first speed (second speed). For this purpose, the stream of imbricated stacks is accelerated to the second speed and is conveyed past a retarding device, which comprises a belt moving at the first speed and being arranged to hold back the upper product of each product pair, while the lower product of the pair is conveyed onwards at the second speed. The upper product is released by the retarding device as soon as a following product pair reaches it.
The spacing between the scales (single products) of such an established imbricated stream is dependent on the ratio of first and second speed and on the scale spacing in the stream of imbricated stacks being supplied to the transformation. If the scale spacing in the supplied stream of product pairs is irregular, then this is also the case in the imbricated stream being established by the transformation.
A device for making an imbricated stream more regular is known from EP 0 254 851 B1. According to this publication, a stream of imbricated products is transported into a stretch constituting a kink in the transport path and not being equipped with active conveying means. Along this stretch the products are stopped by a stop located immediately upstream of the kink. Driving pins arranged on driving wheels deviate the leading zone of every stopped product at a predefined cadence out of the action range of the stop, press it against a belt conveyor aligned in the new conveying direction and guide it into a clamping gap between this belt conveyor and a transport roller engaging the upper side of the product such transporting the product onwards.
The regularizing effect of the device in accordance with EP-254851 is limited; substantial irregularities cannot be equalized. If after the release of a product by the stop, there isn't another product lined up at the stop within one cycle, there will be too large of a distance between the late scale and the preceding one. If several products accumulate at the stop they will usually be conveyed onwards together, because they are driven forward from above by the driving pins and from below by the belt conveyor. Narrowing the gap formed by the stop is supposed to prevent simultaneous release of two products. However, this only works for mechanically robust products. Separating single products from product pairs or from a product stack is possible only with difficulty or not at all.
The operating principle of the device according to EP254851 calls for both actively driven driving pins and transport rollers as well as for a kink in the conveying direction. Therefore it requires a relatively complicated mechanical construction.